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Intention and the omission bias: Omissions perceived as nondecisions
acta psychologica ELSEVIER
Acta Psychologica 93 (1996) 161 - 172
Intention and the omission bias: Omissions perceived as nondecisions Johanna H. Kordes-de Vaal * Department of Cognitice Psychology, Free University, De Boelelaan 1111, 1081 HV Amsterdam, The Netherlands
Abstract People often evaluate a decision to commit an action more negatively than a decision to omit an action, given that both decisions have the same negative consequence. This phenomenon is called the omission bias. In the present experiments, subjects were not asked to justify their judgments in view of doubts about whether the processes underlying decision making are open to introspection. Instead, they were asked to rate an agent's immorality - or the anger evoked by the employer of the agent - as well as the agent's intention, causality, and responsibility for either a commission or an omission version of several scenarios. The results of the three experiments suggest that the basis of the omission bias is a difference in perceived causality, making the outcome of an omission appear less intended than the outcome of a commission. This reduction in perceived intention for outcomes of omissions might make the evaluation of someone's behavior less negative.
PsycINFO classification: 2340;
2360; 3020
Keywords: Omission bias; Immorality; Intention; Causality; Responsibility
1. Introduction An important issue in decision making research concerns the appropriate criteria for evaluating the quality of a decision. According to consequentialist theories (for example, expected utility theory and utilitarianism), expected consequences should determine decisions (Baron, 1994); yet, subjective evaluations of decisions sometimes deviate from this prescription. For example, people often evaluate a decision to commit an action (a
* E-mail: [email protected], Tel.: + 31 20 4448799, Fax: + 3 l 20 4448832. 0001-6918/96/$15.00 Copyright © 1996 Elsevier Science B.V. All rights reserved. PH S 0 0 0 1 - 6 9 1 8 ( 9 6 ) 0 0 0 2 7 - 3
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commission) more negatively than a decision to omit an action (an omission), when given that either decision has the same negative consequence. This phenomenon is called the omission bias (Spranca et al., 1991). Kahneman and Tversky (1982) were among the first researchers to compare people's reactions to acts and nonacts. They found that when imagining a hypothetical scenario with a bad outcome, subjects reported greater regret for acting than for not acting. Landman (1988) replicated these results and observed a similar pattern in the case of joy in positive outcomes. Subjects imagined experiencing greater joy for acts than for nonacts, although the difference was not as strong as for feelings of regret. Spranca et al. (1991) found that action was evaluated more positively than inaction when it led to the 'least bad' outcome and more negatively than inaction when it led to the worst outcome. They called this the 'exaggeration effect', since action appeared to exaggerate the feelings about an outcome, irrespective of whether these feelings were positive or negative. The general question addressed by this paper is why omissions and commissions are evaluated differently, given that the consequences are the same for either option. Ritov and Baron (1992) proposed that the decision maker's preference for omission may result from unwillingness to choose between the available options. Likewise, Janis and Mann (1977) argued that " a decision maker under pressure to make a vital decision will typically find it painful to commit himself, because there are some expected costs and risks no matter which course of action he chooses. One way of coping with such a painful dilemma is to avoid making a decision" (p. 6). If an omission is actually perceived as a nondecision rather than a deliberate choice 'not to act', this (non)decision may be evaluated less negatively - in case of a bad outcome - because there has not been an intentional commitment to one of the options. It could be that the omission bias is due to a perceived difference in intention. In order to study this possibility, Spranca et al. (1991) attempted to hold intention constant in the commission and omission versions of their scenarios. In this case, intention is the readiness to act, not to act, or to attempt to act, so as to realize a desired state of affairs (Brewer, 1977). They hypothesized that the omission bias would disappear when the intentions for omission and commission were held constant. However, their subjects might nevertheless have experienced a difference in intention between omission and commission, due to overgeneralization of the heuristic (Baron, 1988) that there is more intention involved in acting than in not acting. In one of the scenarios used by Spranca et al. (1991), a tennis player has to play a game against Lendl the next day. He knows that Lendl is allergic to Cayenne pepper and he also recalls that the house dressing served in the dining room contains Cayenne pepper. His intention is to have Lendl consume the house dressing. In the omission version, Lendl orders the house dressing himself and his opponent does not warn him of the Cayenne pepper. In the commission version, Lendl's opponent recommends that he try the house dressing, which he does accordingly. A significant number of subjects showed an omission bias. However, in these experiments, subjects gave immorality ratings (between 0 and - 100) for the different versions of the scenarios and every subject who gave a higher rating for the commission than for the omission was said to show an omission bias, even when the difference was only one single point.
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Most subjects argued that their perception of the agent's causal role affected their moral judgments, and many of them also mentioned a perceived difference in responsibility as a reason for the differences between the moral judgments regarding omissions and commissions. In their second experiment, using almost the same scenarios, Spranca et al. (1991) asked subjects explicitly about possible differences in intention. Although almost all subjects rated intention in the commission and omission versions as equivalent, the omission bias was still significantly present. In sum, the results of the first two experiments of Spranca et al. (1991) suggest that the omission bias is caused by a perceived difference in causality, responsibility, or both, and not by a perceived difference in intention. Yet, there has been a long standing debate about whether the processes underlying decision making are open to introspection. Evans (1989) suggested that many biases may be due to subconscious heuristics which guide selective encoding of psychologically 'relevant' features of the problem. According to Wason and Evans (1975), these subconscious processes are not open to introspection, and the reasons people give for their decisions reflect a tendency to construct a justification of their behavior consistent with their knowledge of the situation. They called this the dual processing theory. Results of the experiments of Nisbett and Wilson (1977) indeed show that people do not always know which stimuli are responsible for their responses. When subjects are asked to compare an omission and a commission, it is possible that they give different ratings to come up to expectations. Thus. in the present experiment, subjects were presented with only one version of each scenario, either the omission or the commission. Immorality ratings were compared between subjects. Because of the above-mentioned reasons, subjects were not asked for justifications. Instead, they were asked to give ratings for intention, causality, and responsibility. Because it is unclear if these concepts have separate meanings or that their meanings overlap, subjects were asked to give ratings for all three concepts, so that correlations could be calculated within subjects. If differences in perceived intention are relevant for judgements of immorality, the omission bias should disappear when perceived intention is equivalent for an omission and a commission, even when there is a difference in perceived causality, responsibility. or both. However, when perceived intention is not equivalent for an omission and a commission, the omission bias might be present.
2. Experiment 1 2.1. Method 2.1.1. Subjects
Seventy-four undergraduate students from the Free University of Amsterdam participated in this experiment as part of a paper-and-pencil session with the duration of one hour. They were paid Dfl. 12.50 (about US$7.50) for their participation. 2.1.2. Procedure
Two scenarios were adapted from those used by Spranca et al. (Experiment 1, 1991), and translated into Dutch (see Appendix A). Subjects received one version of Scenario 1
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and one version of Scenario 2. Subjects were divided into four groups. One group saw two omission versions (n = 18), another group saw two commission versions (n = 18), a third (n = 19) and forth (n = 19) group saw the omission version of one scenario and the commission version of the other scenario. The order of presentation of the two scenarios was counterbalanced. After reading a scenario, the subjects were asked to rate the immorality of the agent's behavior on a scale from 0 (not immoral at all) to 100 (as immoral as it is possible to be in this situation), as in Experiments 1 and 2 of Spranca et al. (1991). After completing some unrelated tests so as to make it less likely that they would remember their immorality ratings, and after reading the scenarios for a second time, the subjects were asked the following three questions: A. Give a rating between 0 and 100 to indicate the degree of intention you think was involved in the behavior of the agent in the scenario (0 = absolutely no intention involved, 100 = completely intended). B. To what degree did the behavior of the agent in the scenario cause the event? Give a percentage (0-100%).
C. To what degree was the agent in the scenario responsible for what happened? Give a rating between 0 and 100 (0 --- absolutely not responsible, 100 = completely responsible). 2.2. Results The results of the t-tests are shown in Table 1. A one-tailed alpha level of 0.05 was used for all statistical tests. As in Experiments 1 and 2 of Spranca et al. (1991), an omission bias was still observed, since - on the average - commissions were perceived as more immoral than omissions. Overall, the order in which the scenarios were presented did not significantly affect immorality ratings.
Table 1 M e a n ratings for the omission a n d c o m m i s s i o n versions M e a n ratings Scenario The tennis t o u r n a m e n t Omission Commission t The witness Omission Commission t
Intention
Causality
Responsibility
Immorality
85.7 (21.1) 99.1 (2.6) 3.8 * *
60.5 (38.5) 91.4 (14.7) 4.6 * *
61.8 (34.1) 94. l (11.1) 5.5 * *
73.2 (26.1) 83.9 (23.3) 1.9 *
81.8 (21.4) 96.1 (8.7) 3.8 * *
50.4 (39.0) 88.5 (22.4) 5.2 * *
63.9 (35. l) 89.3 (22.6) 3.7 * *
83.5 (22.4) 93.0 (I 3.1) 2.2 *
Note: Standard deviations are s h o w n in parentheses. * p < 0.05, * * p < 0 . 0 1 .
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The results that are presented in Table 1 show that there was also a significant difference in intention ratings for both scenarios. The average intention ratings for the commissions were higher than for the omissions. This result deviates from that of Experiment 2 of Spranca et al. (1991), in which most subjects failed to perceive a difference in intention between the omission and commission versions. Table 1 also shows a significant difference in causality and responsibility ratings for both scenarios. Again, the average ratings for the commission versions were higher than those for the omission versions. For both scenarios, correlations between various ratings were all significant ( p _< 0.01). For Scenario 1, the correlations between immorality ratings and the other three ratings amounted to 0.32, 0.36, and 0.41 for intention, causality, and responsibility, respectively. For Scenario 2, these correlations were 0.40, 0.43, and 0.41. 2.3. Discussion
The results show evidence for an omission bias. However, since the ratings of all potential contributions correlated, these results cannot distinguish between the contribution of intention, causality, and responsibility in causing the omission bias. The difference in perceived intention persisted. This suggests that subjects overgeneralized the heuristic that there is more intention involved in acting than in not acting for situations were this was not the case. In an attempt to find out whether the use of this heuristic caused the difference in perceived intention between the omission and commission versions of the two scenarios in Experiment 1, the omission version of Scenario 1 was changed into a commission version without a causal relation with the occurrence, while the commission version was left unchanged. Thus, two commissions were compared. In both versions the agent had the same intention, and in both versions he acted in the same way. The difference was that in one (causal) version the agent's commission caused the bad occurrence, and in the other (noncausal) version something else caused the bad occurrence. The aim of Experiment 2 was to find out whether the difference in perceived intention between two versions of a scenario disappeared when subjects would be unable to use the above-mentioned heuristic.
3. Experiment 2 3. I. Method 3.1.1. Subjects
Eighty undergraduate students from the Free University of Amsterdam participated in this experiment as part of a paper-and-pencil session with the duration of one hour. They were paid Dfl. 12.50 (about US$7.50) for their participation. 3.1.2. Procedure
The procedure used was the same as in Experiment 1. Subjects received one of two versions of a scenario (see Appendix A). The two versions of the scenario only differed
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Table 2 Mean ratings for the causal and noncausal version Mean ratings Version
Intention
Causality
Responsibility
Immorality
Causal Noncausal t
99.3 (3.5) 86.8 (26.9) 8.5 * *
90.0 (24.1) 8.5 (14.2) 336.0 * ~
95.6 (13.7) 8.4 (15.3) 723.0 * *
91.0 (13.2) 78.3 (20.0) 11.2 * "
Note: Standard deviations are shown in parentheses. p < 0.01. *
*
in the presence versus absence of a causal link between the agent's behavior in the scenario and the occurrence. After reading the scenario, the subjects were asked to rate the immorality of the agent's behavior on a scale from 0 (not immoral at all) to 100 (as immoral as it is possible to be in this situation). After completing some unrelated tests to make it less likely that they would remember their immorality rating, and after reading the scenario for a second time, subjects were asked to rate intention, causality, and responsibility. 3.2. Results Table 2 shows the average ratings for the causal and noncausal versions of the scenario. A one-tailed alpha level o f 0.05 was used for all statistical tests. In contrast with m y expectation, a t-test showed a significant difference between the mean ratings of perceived intention ( p < 0.005). The differences between the means o f the other three ratings (i.e., immorality, causality, and responsibility) were also significant (see Table 2). In sum, the means for all four ratings were higher for the causal version than for the noncausal version. The correlation between intention ratings and immorality ratings was not significant, r = 0.113, p = 0.159, which could reflect a ceiling effect. A significant correlation was found between ratings o f intention and causality, r = 0.26, p = 0.010, and between ratings of intention and responsibility, r = 0.23, p = 0.005. The ratings of causality and responsibility were almost identical, r = 0.93, p < 0.001. 3.3. Discussion Although subjects were not able to use the heuristic that there is more intention involved in acting than in not acting, because both versions of the scenario involved action, the results show a significant difference in intention ratings between the causal and noncausal versions of the scenario. This difference, as well as the significant correlation between intention and causality ratings, suggests that perceived intention is influences by perceived causality. In other words, people seem to think that when someone's behavior has a strong causal link with its outcome, this behavior involved more intention for that particular outcome than when this causal link is less strong. W h e n a difference in perceived causality, responsibility, or both would suffice to
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bring about a difference in perceived immorality, the average ratings for causality, responsibility, and immorality would be expected to show differences of the same magnitude between the causal and noncausal version. However, looking at Table 2 we can see that the average immorality ratings for the causal and noncausal version differ much less than the average causality and responsibility ratings do. The difference in average immorality ratings is more like the magnitude of the difference in average intention ratings between the causal and noncausal version. It may be that perceived causality is only able to bring about an omission bias with perceived intention as an intermediate. Although in Experiment 2 the agent had the same intention in both the causal and noncausal version, subjects still perceived them differently. In an attempt to avoid such differential perceived intention in Experiment 3, I used scenarios for which - in either version - the agent absolutely did not intent to bring about the negative consequence. To accomplish this, I constructed several scenarios in which the agent made a slip or a lapse. These are unintended execution failures which primarily happen when one is performing a largely automatic task (Reason, 1990). The expectation was that slips of commission would be perceived as stronger causal candidates than slips of omission, because commissions are more salient (Taylor, 1982), As the correlations between ratings for causality and responsibility were highly significant for Experiments 1 and 2, the expectation was that an agent would also be perceived as being more responsible for a commission than for an omission. If this reasoning proved to be valid, it would enable a test of whether a difference in perceived causality, responsibility, or both suffices to bring about an omission bias or if a difference in perceived intention is necessary as an intermediate.
4. Experiment 3 4.1. Method 4.1. I. Subjects The same subjects participated as in Experiment 2. 4.1.2. Procedure The procedure was roughly the same as that in Experiments i and 2. Three scenarios were used, because when only one scenario is used the results could be due to other aspects of the story than the manipulated aspects. When all scenarios show the same results, it is more likely that the intended manipulation succeeded. A forth scenario (the taxidriver) was presented to the subjects, for which the results showed a commission bias. When 45 additional subjects were asked to comment upon their ratings for this scenario, they mentioned the loss of money - the outcome mentioned in the scenario equally often for either version. In addition, they mentioned the loss of a customer and discredit to the firm's reputation for the omission version. With respect to the commission version they only mentioned the loss of a potential customer, which is a much less unfavorable consequence. Thus the consequences were not considered to be the same for
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the two versions. Therefore, I did not include the results for this scenario in the present report. The two versions of the three scenarios differed with respect to whether the slip or lapse was an omission or a commission (see Appendix B). The consequences of the agent's behavior were the same for the two versions of each scenario. Subjects were divided into two groups. One group of subjects (n = 40) received the omission versions of Scenarios 1 and 2 and the commission version of Scenario 3, and another group of subjects (n = 40) received the commission versions of Scenarios 1 and 2 and the omission version of Scenario 3. Because unintended slips or lapses were not expected to be judged as immoral, subjects were asked to give immediate ratings on how angry they expected the employer of the agent to be (0 = absolutely not angry, 100--extremely angry). Prior to each scenario a standard scenario was presented to prevent subjects from anchoring their anger ratings on the ratings given for the previous relevant scenario. If no standard scenario was used, the influence of the omission/commission manipulation might be reduced for every next scenario. One of the scenarios - Scenario i - went as follows: A nurse is about to give a patient his necessary medicine when she is called away for an emergency. When she comes back she has forgotten where she left off and forgets to give the medicine to the patient. The patient has an unbearable stomachache the whole night through (omission). A nurse has just given a patient his necessary medicine when she is called away for an emergency. When she comes back she has forgotten where she left off and gives the medicine to the patient for a second time. The patient has an unbearable stomachache the whole night through (commission). Subjects were asked to rate intention, causality, and responsibility after all scenarios had been presented, and after they had read the three scenarios for a second time. Before this, the subjects completed various unrelated tasks so that they would be less likely to remember earlier anger ratings. 4.2. Results The three scenarios were too different to compare an omission version of one scenario with a commission version of another scenario within subjects. The results of the t-tests of Experiment 3 for between-subjects comparison of the omission and commission versions of the three scenarios are shown in Table 3. A two-tailed alpha level of 0.05 was used for all statistical tests. There was no significant difference in the ratings for intention and anger between the omission and commission versions. This was true for all three scenarios (see Table 3). For Scenarios 1 and 3, there was a significant difference between the causality ratings for the different versions. As expected, the commission versions were perceived as showing stronger agent causality than the omission versions. The responsibility ratings were also higher for the commission versions than for the omission versions, but this difference was only significant for Scenario 3. For all three scenarios, the ratings of
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Table 3 Mean ratings for the unintendedomission and unintendedcommissionversions Mean ratings Scenario The nurse (1) Omission Commission t The auto-mechanic(2) Omission Commission t The mechanic(3) Omission Commission t
Intention
Causality
Responsibility
Anger
2.8 (12.8) 2.6 (11.3) 0.0
78.1 (26.5) 89.6 (17.7) 5.2 *
81.3 (22.4) 88.0 (15.6) 2.4
82.3 (16.0) 79.2 (19.7) 0.6
6.3 (18.6) 3.8 (8.1) 0.6
82.6 (23.4) 84.7 (24.7) 0.2
79.6 (20.7) 84.9 (16. l) 1.6
80.5 (19.8) 78.9 (16.4) 0.1
8.9 (15.9) 7.0 (20.7) 0.2
63.9 (27.7) 77.7 (25.8) 5.3 *
67.3 (27.4) 79.6 (23.6) 4.7 ~
78.6 (14.3) 79. l (18.0) 0.0
Note: Standard deviationsare shown in parentheses. * p < 0.05.
causality and responsibility were significantly correlated ( p < 0.001, for all 3 scenarios). In order, the correlations for Scenarios 1 through 3 were 0.472, 0.525, and 0.746. 4.3. Discussion
The results show that a significant difference in perceived causality, in the absence of a significant difference in perceived intention, did not suffice to cause an omission bias. These results suggest that a difference in perceived causality may only suffice to bring about an omission bias with perceived intention as an intermediate.
5. G e n e r a l d i s c u s s i o n
In sum, the results of the three experiments suggest that the basis of the omission bias is a difference in perceived causality - probably caused by the fact that commissions are more salient than omissions - making the outcome of an omission appear less intended than the outcome of a commission. In other words, people seem to think that if you want something to happen, you can make it happen: If something is not, or in a lesser degree, caused by your behavior, you did not intend it to happen as much as when something came about because of what you did or did not do. Because of the reduced strength of the perceived causal link between an omission and its consequence, an omission may usually be perceived as a nondecision, or at least as a less intended decision than a commission. In case of the three scenarios of Experiment 3, omissions as well as commissions were perceived as nondecisions, shown by the fact that intention ratings were low for both versions. This may be the reason that a difference in perceived intention was not found for these scenarios.
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A difference in perceived intention might not only affect judgments of immorality, or anger expected to evoke by other people, but also expected feelings of regret, guilt, and general judgments of the quality of a decision. A difference in perceived intention without a difference in perceived causality might suffice to cause a different evaluation of omissions and commissions, but to test this hypothesis a further scenario is needed for which the two versions do not differ in causality. Such a scenario is hard to design, because commissions are usually more salient and thus perceived as stronger causal candidates than omissions (Taylor, 1982). According to Brewer (1977), intention is one of the mechanisms affecting the perception of congruence between an action and its consequences, especially when a given action has multiple equiprobable outcomes. Thus when intention is manipulated, presumably perceived causality will differ as well. The correlations between causality and responsibility ratings were significant for all experiments ( p < 0.001), suggesting that the meaning of the words 'causality' and 'responsibility' largely overlap. As the results of Scenarios 1 and 2 of Experiment 3 show, the omission bias is not only absent when perceived intention is low for both versions, but the effect may even reverse in that commissions are perceived as evoking less anger than omissions. A possible explanation for this result is that people who omit to do what is part of their responsibility might be regarded as slack.
Acknowledgements Thanks to Andries Sanders, Willem Albert Wagenaar, and two anonymous reviewers for valuable comments on an earlier version of this article, and to Gideon Keren for fruitful discussions on this subject.
Appendix A A.1. Scenario 1: The tennis tournament
John West plays tennis at the TEAN tennis club two or three times a week. John is the best player at the club, but he is not good enough to play professionally. The club holds an annual tennis tournament, for which a big-name player is usually invited to attract a large audience. The first prize is Dfl. 50,000 and the prize for the runner-up is Dfl. 10,000. This year Paul Haarhuis agreed to play in the tournament. John and Paul quickly advanced to the finals. John would of course love to win, but he realizes that he is at a large disadvantage. The tradition at TEAN is that both finalists meet for dinner at the club before the final the next morning. While getting dressed for dinner, John remembers that Paul is allergic to Cayenne pepper. He also recalls that the house dressing served in the dining room contains Cayenne pepper. John beliefs that the only way to beat Paul is to have him eat this dressing.
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Omission (Experiment 1). John is about to recommend the house dressing, but before John can say anything, Paul orders the house dressing himself. John says nothing. Paul gets a stomachache and John wins the match. Commission with causality (Experiment 1 and 2). Before Paul makes a choice, John recommends that Paul try the house dressing. Paul orders it and gets a stomachache. John wins the match. Commission without causality (Experiment 2). Before Paul makes a choice, John recommends that Paul try the house dressing. However, Paul orders the Italian dressing. Unknown to either man, this dressing also contains Cayenne pepper. Paul gets a stomachache and John wins the match. A.2. Scenario 2: The witness
Peter, a resident of the province Zeeland, is driving through a small town in Brabant. At a four-way intersection, he gets into a small accident with a town resident named Tom. The accident came about like this: Travelling north, Tom approached the four-way intersection. The trafficlight was red, but he failed to slow down. Meanwhile, Peter started moving again, because the light had turned green, and he crossed the intersection traveling east. Peter saw a car, Tom' s, crossing the intersection. Peter slammed on his brakes, but could not avoid hitting Tom's car as it passed in front of him. The accident was clearly Tom's fault, because he ignored a red light. However, because no other cars were present at the time of the accident, the police might believe that Peter ignored a red light. Immediately after the accident, both men exclaimed that it was the other's fault. When the police came, Peter told them that the accident had been caused by Tom's failure to stop. Tom told the police that the accident was caused by Peter's failure to stop. Unknown to either man, there was an eyewitness to the accident, Ellen. Like Tom, Ellen is also a resident of the town. She thought, " I know the accident is Tom's fault, but I know Tom and do not want him to be punished". Omission. Ellen is about to tell the police that Peter ignored the red light, when the police charge Peter with failure to stop. Ellen does not say anything and Peter has to pay Dfl. 5,000 for damage to Tom's car. Commission. Ellen tells the police that it was Peter who ignored the red light, not Tom. The police charge Peter with failure to stop, and he has to pay Dfl. 5,000 for damage to T o m ' s car.
Appendix B B.1. Scenario I: The nurse
See the Method section of Experiment 3.
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B.2. Scenario 2: The auto-mechanic Omission. A mechanic is repairing a motor of a new type. He does not realize that this motor differs from the old type that he is used to. Because of this, he fails to fix an extra part that is essential for good functioning of the motor. The motor jams and the loss for the business works out to Dfl. 5,000. Commission. A mechanic is repairing a motor of a new type. He does not realize that this motor differs from the old type that he is used to. Because of this, he fixes a part as he would for the old type of motor in this motor. The motor jams and the loss for the business works out to Dfl. 5,000. B.3. Scenario 3: The mechanic Omission. A mechanic has adjusted the traffic lights at 2:00 a.m. in the morning to disturb the traffic as little as possible. In a hurry, because he wants to go to bed, he neglects to reconnect the lights to the system, so that the yellow flashing light keeps burning. The next morning a collision takes place, resulting in a lot of auto body damage, for which the costs are charged to the mechanic's company. Commission. A mechanic has adjusted the traffic lights at 2:00 a.m. in the morning to disturb the traffic as little as possible. In a hurry, because he wants to go to bed, he quickly sets the timer so that the traffic light would start working before rush hour. He sets it at 8:30 a.m. instead of 6:30 a.m., however. The next morning a collision takes place, resulting in a lot of auto body damage, for which the costs are charged to the mechanic's company.
References Baron, J., 1988. Thinking and deciding. New York: Cambridge University Press. Baron, J., 1994. Nonconsequentialist decisions. Behavioral and Brain Sciences 17, 1-42. Brewer, M.B., 1977. An information-processing approach to attribution of responsibility. Journal of Experimental Social Psychology 13, 58-69. Evans, J.St.B.T., 1989. Bias in human reasoning: Causes and consequences. East Sussex: Erlbaum. Janis, I.L. and L. Mann, 1977. Decision making. A psychological analysis of conflict, choice, and commitment. New York: The Free Press. Kahneman, D. and A. Tversky, 1982. The psychology of preferences. Scientific American 246, 160-173. Landman, J., 1988. Regret and elation following action and inaction: Affective responses to positive versus negative outcomes. Personality and Social Psychology Bulletin 13, 524-536. Nisbett, R. and T.D. Wilson, 1977. Telling more than we can know: Verbal reports on mental processes. Psychological Review 84, 231-259. Reason, J., 1990. Human error. New York: Cambridge University Press. Ritov, 1. and J. Baron, 1992. Status-quo and omission biases. Journal of Risk and Uncertainty 5, 49-61. Spranca, M., E. Minsk and J. Baron, 1991. Omission and commission in judgment and choice. Journal of Experimental Social Psychology 27, 76-105. Taylor, S.E., 1982. "The availability bias in social perception and interaction'. In: Kahneman, D., P. Slovic and A. Tversky (Eds.), Judgment under uncertainty: Heuristics and biases. New York: Cambridge University Press. Wason, P.C. and J.St.B.T. Evans, 1975. Dual processing in reasoning? Cognition 3, 141-154.
Acta Psychologica 93 (1996) 161 - 172
Intention and the omission bias: Omissions perceived as nondecisions Johanna H. Kordes-de Vaal * Department of Cognitice Psychology, Free University, De Boelelaan 1111, 1081 HV Amsterdam, The Netherlands
Abstract People often evaluate a decision to commit an action more negatively than a decision to omit an action, given that both decisions have the same negative consequence. This phenomenon is called the omission bias. In the present experiments, subjects were not asked to justify their judgments in view of doubts about whether the processes underlying decision making are open to introspection. Instead, they were asked to rate an agent's immorality - or the anger evoked by the employer of the agent - as well as the agent's intention, causality, and responsibility for either a commission or an omission version of several scenarios. The results of the three experiments suggest that the basis of the omission bias is a difference in perceived causality, making the outcome of an omission appear less intended than the outcome of a commission. This reduction in perceived intention for outcomes of omissions might make the evaluation of someone's behavior less negative.
PsycINFO classification: 2340;
2360; 3020
Keywords: Omission bias; Immorality; Intention; Causality; Responsibility
1. Introduction An important issue in decision making research concerns the appropriate criteria for evaluating the quality of a decision. According to consequentialist theories (for example, expected utility theory and utilitarianism), expected consequences should determine decisions (Baron, 1994); yet, subjective evaluations of decisions sometimes deviate from this prescription. For example, people often evaluate a decision to commit an action (a
* E-mail: [email protected], Tel.: + 31 20 4448799, Fax: + 3 l 20 4448832. 0001-6918/96/$15.00 Copyright © 1996 Elsevier Science B.V. All rights reserved. PH S 0 0 0 1 - 6 9 1 8 ( 9 6 ) 0 0 0 2 7 - 3
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commission) more negatively than a decision to omit an action (an omission), when given that either decision has the same negative consequence. This phenomenon is called the omission bias (Spranca et al., 1991). Kahneman and Tversky (1982) were among the first researchers to compare people's reactions to acts and nonacts. They found that when imagining a hypothetical scenario with a bad outcome, subjects reported greater regret for acting than for not acting. Landman (1988) replicated these results and observed a similar pattern in the case of joy in positive outcomes. Subjects imagined experiencing greater joy for acts than for nonacts, although the difference was not as strong as for feelings of regret. Spranca et al. (1991) found that action was evaluated more positively than inaction when it led to the 'least bad' outcome and more negatively than inaction when it led to the worst outcome. They called this the 'exaggeration effect', since action appeared to exaggerate the feelings about an outcome, irrespective of whether these feelings were positive or negative. The general question addressed by this paper is why omissions and commissions are evaluated differently, given that the consequences are the same for either option. Ritov and Baron (1992) proposed that the decision maker's preference for omission may result from unwillingness to choose between the available options. Likewise, Janis and Mann (1977) argued that " a decision maker under pressure to make a vital decision will typically find it painful to commit himself, because there are some expected costs and risks no matter which course of action he chooses. One way of coping with such a painful dilemma is to avoid making a decision" (p. 6). If an omission is actually perceived as a nondecision rather than a deliberate choice 'not to act', this (non)decision may be evaluated less negatively - in case of a bad outcome - because there has not been an intentional commitment to one of the options. It could be that the omission bias is due to a perceived difference in intention. In order to study this possibility, Spranca et al. (1991) attempted to hold intention constant in the commission and omission versions of their scenarios. In this case, intention is the readiness to act, not to act, or to attempt to act, so as to realize a desired state of affairs (Brewer, 1977). They hypothesized that the omission bias would disappear when the intentions for omission and commission were held constant. However, their subjects might nevertheless have experienced a difference in intention between omission and commission, due to overgeneralization of the heuristic (Baron, 1988) that there is more intention involved in acting than in not acting. In one of the scenarios used by Spranca et al. (1991), a tennis player has to play a game against Lendl the next day. He knows that Lendl is allergic to Cayenne pepper and he also recalls that the house dressing served in the dining room contains Cayenne pepper. His intention is to have Lendl consume the house dressing. In the omission version, Lendl orders the house dressing himself and his opponent does not warn him of the Cayenne pepper. In the commission version, Lendl's opponent recommends that he try the house dressing, which he does accordingly. A significant number of subjects showed an omission bias. However, in these experiments, subjects gave immorality ratings (between 0 and - 100) for the different versions of the scenarios and every subject who gave a higher rating for the commission than for the omission was said to show an omission bias, even when the difference was only one single point.
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Most subjects argued that their perception of the agent's causal role affected their moral judgments, and many of them also mentioned a perceived difference in responsibility as a reason for the differences between the moral judgments regarding omissions and commissions. In their second experiment, using almost the same scenarios, Spranca et al. (1991) asked subjects explicitly about possible differences in intention. Although almost all subjects rated intention in the commission and omission versions as equivalent, the omission bias was still significantly present. In sum, the results of the first two experiments of Spranca et al. (1991) suggest that the omission bias is caused by a perceived difference in causality, responsibility, or both, and not by a perceived difference in intention. Yet, there has been a long standing debate about whether the processes underlying decision making are open to introspection. Evans (1989) suggested that many biases may be due to subconscious heuristics which guide selective encoding of psychologically 'relevant' features of the problem. According to Wason and Evans (1975), these subconscious processes are not open to introspection, and the reasons people give for their decisions reflect a tendency to construct a justification of their behavior consistent with their knowledge of the situation. They called this the dual processing theory. Results of the experiments of Nisbett and Wilson (1977) indeed show that people do not always know which stimuli are responsible for their responses. When subjects are asked to compare an omission and a commission, it is possible that they give different ratings to come up to expectations. Thus. in the present experiment, subjects were presented with only one version of each scenario, either the omission or the commission. Immorality ratings were compared between subjects. Because of the above-mentioned reasons, subjects were not asked for justifications. Instead, they were asked to give ratings for intention, causality, and responsibility. Because it is unclear if these concepts have separate meanings or that their meanings overlap, subjects were asked to give ratings for all three concepts, so that correlations could be calculated within subjects. If differences in perceived intention are relevant for judgements of immorality, the omission bias should disappear when perceived intention is equivalent for an omission and a commission, even when there is a difference in perceived causality, responsibility. or both. However, when perceived intention is not equivalent for an omission and a commission, the omission bias might be present.
2. Experiment 1 2.1. Method 2.1.1. Subjects
Seventy-four undergraduate students from the Free University of Amsterdam participated in this experiment as part of a paper-and-pencil session with the duration of one hour. They were paid Dfl. 12.50 (about US$7.50) for their participation. 2.1.2. Procedure
Two scenarios were adapted from those used by Spranca et al. (Experiment 1, 1991), and translated into Dutch (see Appendix A). Subjects received one version of Scenario 1
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and one version of Scenario 2. Subjects were divided into four groups. One group saw two omission versions (n = 18), another group saw two commission versions (n = 18), a third (n = 19) and forth (n = 19) group saw the omission version of one scenario and the commission version of the other scenario. The order of presentation of the two scenarios was counterbalanced. After reading a scenario, the subjects were asked to rate the immorality of the agent's behavior on a scale from 0 (not immoral at all) to 100 (as immoral as it is possible to be in this situation), as in Experiments 1 and 2 of Spranca et al. (1991). After completing some unrelated tests so as to make it less likely that they would remember their immorality ratings, and after reading the scenarios for a second time, the subjects were asked the following three questions: A. Give a rating between 0 and 100 to indicate the degree of intention you think was involved in the behavior of the agent in the scenario (0 = absolutely no intention involved, 100 = completely intended). B. To what degree did the behavior of the agent in the scenario cause the event? Give a percentage (0-100%).
C. To what degree was the agent in the scenario responsible for what happened? Give a rating between 0 and 100 (0 --- absolutely not responsible, 100 = completely responsible). 2.2. Results The results of the t-tests are shown in Table 1. A one-tailed alpha level of 0.05 was used for all statistical tests. As in Experiments 1 and 2 of Spranca et al. (1991), an omission bias was still observed, since - on the average - commissions were perceived as more immoral than omissions. Overall, the order in which the scenarios were presented did not significantly affect immorality ratings.
Table 1 M e a n ratings for the omission a n d c o m m i s s i o n versions M e a n ratings Scenario The tennis t o u r n a m e n t Omission Commission t The witness Omission Commission t
Intention
Causality
Responsibility
Immorality
85.7 (21.1) 99.1 (2.6) 3.8 * *
60.5 (38.5) 91.4 (14.7) 4.6 * *
61.8 (34.1) 94. l (11.1) 5.5 * *
73.2 (26.1) 83.9 (23.3) 1.9 *
81.8 (21.4) 96.1 (8.7) 3.8 * *
50.4 (39.0) 88.5 (22.4) 5.2 * *
63.9 (35. l) 89.3 (22.6) 3.7 * *
83.5 (22.4) 93.0 (I 3.1) 2.2 *
Note: Standard deviations are s h o w n in parentheses. * p < 0.05, * * p < 0 . 0 1 .
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The results that are presented in Table 1 show that there was also a significant difference in intention ratings for both scenarios. The average intention ratings for the commissions were higher than for the omissions. This result deviates from that of Experiment 2 of Spranca et al. (1991), in which most subjects failed to perceive a difference in intention between the omission and commission versions. Table 1 also shows a significant difference in causality and responsibility ratings for both scenarios. Again, the average ratings for the commission versions were higher than those for the omission versions. For both scenarios, correlations between various ratings were all significant ( p _< 0.01). For Scenario 1, the correlations between immorality ratings and the other three ratings amounted to 0.32, 0.36, and 0.41 for intention, causality, and responsibility, respectively. For Scenario 2, these correlations were 0.40, 0.43, and 0.41. 2.3. Discussion
The results show evidence for an omission bias. However, since the ratings of all potential contributions correlated, these results cannot distinguish between the contribution of intention, causality, and responsibility in causing the omission bias. The difference in perceived intention persisted. This suggests that subjects overgeneralized the heuristic that there is more intention involved in acting than in not acting for situations were this was not the case. In an attempt to find out whether the use of this heuristic caused the difference in perceived intention between the omission and commission versions of the two scenarios in Experiment 1, the omission version of Scenario 1 was changed into a commission version without a causal relation with the occurrence, while the commission version was left unchanged. Thus, two commissions were compared. In both versions the agent had the same intention, and in both versions he acted in the same way. The difference was that in one (causal) version the agent's commission caused the bad occurrence, and in the other (noncausal) version something else caused the bad occurrence. The aim of Experiment 2 was to find out whether the difference in perceived intention between two versions of a scenario disappeared when subjects would be unable to use the above-mentioned heuristic.
3. Experiment 2 3. I. Method 3.1.1. Subjects
Eighty undergraduate students from the Free University of Amsterdam participated in this experiment as part of a paper-and-pencil session with the duration of one hour. They were paid Dfl. 12.50 (about US$7.50) for their participation. 3.1.2. Procedure
The procedure used was the same as in Experiment 1. Subjects received one of two versions of a scenario (see Appendix A). The two versions of the scenario only differed
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Table 2 Mean ratings for the causal and noncausal version Mean ratings Version
Intention
Causality
Responsibility
Immorality
Causal Noncausal t
99.3 (3.5) 86.8 (26.9) 8.5 * *
90.0 (24.1) 8.5 (14.2) 336.0 * ~
95.6 (13.7) 8.4 (15.3) 723.0 * *
91.0 (13.2) 78.3 (20.0) 11.2 * "
Note: Standard deviations are shown in parentheses. p < 0.01. *
*
in the presence versus absence of a causal link between the agent's behavior in the scenario and the occurrence. After reading the scenario, the subjects were asked to rate the immorality of the agent's behavior on a scale from 0 (not immoral at all) to 100 (as immoral as it is possible to be in this situation). After completing some unrelated tests to make it less likely that they would remember their immorality rating, and after reading the scenario for a second time, subjects were asked to rate intention, causality, and responsibility. 3.2. Results Table 2 shows the average ratings for the causal and noncausal versions of the scenario. A one-tailed alpha level o f 0.05 was used for all statistical tests. In contrast with m y expectation, a t-test showed a significant difference between the mean ratings of perceived intention ( p < 0.005). The differences between the means o f the other three ratings (i.e., immorality, causality, and responsibility) were also significant (see Table 2). In sum, the means for all four ratings were higher for the causal version than for the noncausal version. The correlation between intention ratings and immorality ratings was not significant, r = 0.113, p = 0.159, which could reflect a ceiling effect. A significant correlation was found between ratings o f intention and causality, r = 0.26, p = 0.010, and between ratings of intention and responsibility, r = 0.23, p = 0.005. The ratings of causality and responsibility were almost identical, r = 0.93, p < 0.001. 3.3. Discussion Although subjects were not able to use the heuristic that there is more intention involved in acting than in not acting, because both versions of the scenario involved action, the results show a significant difference in intention ratings between the causal and noncausal versions of the scenario. This difference, as well as the significant correlation between intention and causality ratings, suggests that perceived intention is influences by perceived causality. In other words, people seem to think that when someone's behavior has a strong causal link with its outcome, this behavior involved more intention for that particular outcome than when this causal link is less strong. W h e n a difference in perceived causality, responsibility, or both would suffice to
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bring about a difference in perceived immorality, the average ratings for causality, responsibility, and immorality would be expected to show differences of the same magnitude between the causal and noncausal version. However, looking at Table 2 we can see that the average immorality ratings for the causal and noncausal version differ much less than the average causality and responsibility ratings do. The difference in average immorality ratings is more like the magnitude of the difference in average intention ratings between the causal and noncausal version. It may be that perceived causality is only able to bring about an omission bias with perceived intention as an intermediate. Although in Experiment 2 the agent had the same intention in both the causal and noncausal version, subjects still perceived them differently. In an attempt to avoid such differential perceived intention in Experiment 3, I used scenarios for which - in either version - the agent absolutely did not intent to bring about the negative consequence. To accomplish this, I constructed several scenarios in which the agent made a slip or a lapse. These are unintended execution failures which primarily happen when one is performing a largely automatic task (Reason, 1990). The expectation was that slips of commission would be perceived as stronger causal candidates than slips of omission, because commissions are more salient (Taylor, 1982), As the correlations between ratings for causality and responsibility were highly significant for Experiments 1 and 2, the expectation was that an agent would also be perceived as being more responsible for a commission than for an omission. If this reasoning proved to be valid, it would enable a test of whether a difference in perceived causality, responsibility, or both suffices to bring about an omission bias or if a difference in perceived intention is necessary as an intermediate.
4. Experiment 3 4.1. Method 4.1. I. Subjects The same subjects participated as in Experiment 2. 4.1.2. Procedure The procedure was roughly the same as that in Experiments i and 2. Three scenarios were used, because when only one scenario is used the results could be due to other aspects of the story than the manipulated aspects. When all scenarios show the same results, it is more likely that the intended manipulation succeeded. A forth scenario (the taxidriver) was presented to the subjects, for which the results showed a commission bias. When 45 additional subjects were asked to comment upon their ratings for this scenario, they mentioned the loss of money - the outcome mentioned in the scenario equally often for either version. In addition, they mentioned the loss of a customer and discredit to the firm's reputation for the omission version. With respect to the commission version they only mentioned the loss of a potential customer, which is a much less unfavorable consequence. Thus the consequences were not considered to be the same for
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the two versions. Therefore, I did not include the results for this scenario in the present report. The two versions of the three scenarios differed with respect to whether the slip or lapse was an omission or a commission (see Appendix B). The consequences of the agent's behavior were the same for the two versions of each scenario. Subjects were divided into two groups. One group of subjects (n = 40) received the omission versions of Scenarios 1 and 2 and the commission version of Scenario 3, and another group of subjects (n = 40) received the commission versions of Scenarios 1 and 2 and the omission version of Scenario 3. Because unintended slips or lapses were not expected to be judged as immoral, subjects were asked to give immediate ratings on how angry they expected the employer of the agent to be (0 = absolutely not angry, 100--extremely angry). Prior to each scenario a standard scenario was presented to prevent subjects from anchoring their anger ratings on the ratings given for the previous relevant scenario. If no standard scenario was used, the influence of the omission/commission manipulation might be reduced for every next scenario. One of the scenarios - Scenario i - went as follows: A nurse is about to give a patient his necessary medicine when she is called away for an emergency. When she comes back she has forgotten where she left off and forgets to give the medicine to the patient. The patient has an unbearable stomachache the whole night through (omission). A nurse has just given a patient his necessary medicine when she is called away for an emergency. When she comes back she has forgotten where she left off and gives the medicine to the patient for a second time. The patient has an unbearable stomachache the whole night through (commission). Subjects were asked to rate intention, causality, and responsibility after all scenarios had been presented, and after they had read the three scenarios for a second time. Before this, the subjects completed various unrelated tasks so that they would be less likely to remember earlier anger ratings. 4.2. Results The three scenarios were too different to compare an omission version of one scenario with a commission version of another scenario within subjects. The results of the t-tests of Experiment 3 for between-subjects comparison of the omission and commission versions of the three scenarios are shown in Table 3. A two-tailed alpha level of 0.05 was used for all statistical tests. There was no significant difference in the ratings for intention and anger between the omission and commission versions. This was true for all three scenarios (see Table 3). For Scenarios 1 and 3, there was a significant difference between the causality ratings for the different versions. As expected, the commission versions were perceived as showing stronger agent causality than the omission versions. The responsibility ratings were also higher for the commission versions than for the omission versions, but this difference was only significant for Scenario 3. For all three scenarios, the ratings of
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Table 3 Mean ratings for the unintendedomission and unintendedcommissionversions Mean ratings Scenario The nurse (1) Omission Commission t The auto-mechanic(2) Omission Commission t The mechanic(3) Omission Commission t
Intention
Causality
Responsibility
Anger
2.8 (12.8) 2.6 (11.3) 0.0
78.1 (26.5) 89.6 (17.7) 5.2 *
81.3 (22.4) 88.0 (15.6) 2.4
82.3 (16.0) 79.2 (19.7) 0.6
6.3 (18.6) 3.8 (8.1) 0.6
82.6 (23.4) 84.7 (24.7) 0.2
79.6 (20.7) 84.9 (16. l) 1.6
80.5 (19.8) 78.9 (16.4) 0.1
8.9 (15.9) 7.0 (20.7) 0.2
63.9 (27.7) 77.7 (25.8) 5.3 *
67.3 (27.4) 79.6 (23.6) 4.7 ~
78.6 (14.3) 79. l (18.0) 0.0
Note: Standard deviationsare shown in parentheses. * p < 0.05.
causality and responsibility were significantly correlated ( p < 0.001, for all 3 scenarios). In order, the correlations for Scenarios 1 through 3 were 0.472, 0.525, and 0.746. 4.3. Discussion
The results show that a significant difference in perceived causality, in the absence of a significant difference in perceived intention, did not suffice to cause an omission bias. These results suggest that a difference in perceived causality may only suffice to bring about an omission bias with perceived intention as an intermediate.
5. G e n e r a l d i s c u s s i o n
In sum, the results of the three experiments suggest that the basis of the omission bias is a difference in perceived causality - probably caused by the fact that commissions are more salient than omissions - making the outcome of an omission appear less intended than the outcome of a commission. In other words, people seem to think that if you want something to happen, you can make it happen: If something is not, or in a lesser degree, caused by your behavior, you did not intend it to happen as much as when something came about because of what you did or did not do. Because of the reduced strength of the perceived causal link between an omission and its consequence, an omission may usually be perceived as a nondecision, or at least as a less intended decision than a commission. In case of the three scenarios of Experiment 3, omissions as well as commissions were perceived as nondecisions, shown by the fact that intention ratings were low for both versions. This may be the reason that a difference in perceived intention was not found for these scenarios.
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A difference in perceived intention might not only affect judgments of immorality, or anger expected to evoke by other people, but also expected feelings of regret, guilt, and general judgments of the quality of a decision. A difference in perceived intention without a difference in perceived causality might suffice to cause a different evaluation of omissions and commissions, but to test this hypothesis a further scenario is needed for which the two versions do not differ in causality. Such a scenario is hard to design, because commissions are usually more salient and thus perceived as stronger causal candidates than omissions (Taylor, 1982). According to Brewer (1977), intention is one of the mechanisms affecting the perception of congruence between an action and its consequences, especially when a given action has multiple equiprobable outcomes. Thus when intention is manipulated, presumably perceived causality will differ as well. The correlations between causality and responsibility ratings were significant for all experiments ( p < 0.001), suggesting that the meaning of the words 'causality' and 'responsibility' largely overlap. As the results of Scenarios 1 and 2 of Experiment 3 show, the omission bias is not only absent when perceived intention is low for both versions, but the effect may even reverse in that commissions are perceived as evoking less anger than omissions. A possible explanation for this result is that people who omit to do what is part of their responsibility might be regarded as slack.
Acknowledgements Thanks to Andries Sanders, Willem Albert Wagenaar, and two anonymous reviewers for valuable comments on an earlier version of this article, and to Gideon Keren for fruitful discussions on this subject.
Appendix A A.1. Scenario 1: The tennis tournament
John West plays tennis at the TEAN tennis club two or three times a week. John is the best player at the club, but he is not good enough to play professionally. The club holds an annual tennis tournament, for which a big-name player is usually invited to attract a large audience. The first prize is Dfl. 50,000 and the prize for the runner-up is Dfl. 10,000. This year Paul Haarhuis agreed to play in the tournament. John and Paul quickly advanced to the finals. John would of course love to win, but he realizes that he is at a large disadvantage. The tradition at TEAN is that both finalists meet for dinner at the club before the final the next morning. While getting dressed for dinner, John remembers that Paul is allergic to Cayenne pepper. He also recalls that the house dressing served in the dining room contains Cayenne pepper. John beliefs that the only way to beat Paul is to have him eat this dressing.
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Omission (Experiment 1). John is about to recommend the house dressing, but before John can say anything, Paul orders the house dressing himself. John says nothing. Paul gets a stomachache and John wins the match. Commission with causality (Experiment 1 and 2). Before Paul makes a choice, John recommends that Paul try the house dressing. Paul orders it and gets a stomachache. John wins the match. Commission without causality (Experiment 2). Before Paul makes a choice, John recommends that Paul try the house dressing. However, Paul orders the Italian dressing. Unknown to either man, this dressing also contains Cayenne pepper. Paul gets a stomachache and John wins the match. A.2. Scenario 2: The witness
Peter, a resident of the province Zeeland, is driving through a small town in Brabant. At a four-way intersection, he gets into a small accident with a town resident named Tom. The accident came about like this: Travelling north, Tom approached the four-way intersection. The trafficlight was red, but he failed to slow down. Meanwhile, Peter started moving again, because the light had turned green, and he crossed the intersection traveling east. Peter saw a car, Tom' s, crossing the intersection. Peter slammed on his brakes, but could not avoid hitting Tom's car as it passed in front of him. The accident was clearly Tom's fault, because he ignored a red light. However, because no other cars were present at the time of the accident, the police might believe that Peter ignored a red light. Immediately after the accident, both men exclaimed that it was the other's fault. When the police came, Peter told them that the accident had been caused by Tom's failure to stop. Tom told the police that the accident was caused by Peter's failure to stop. Unknown to either man, there was an eyewitness to the accident, Ellen. Like Tom, Ellen is also a resident of the town. She thought, " I know the accident is Tom's fault, but I know Tom and do not want him to be punished". Omission. Ellen is about to tell the police that Peter ignored the red light, when the police charge Peter with failure to stop. Ellen does not say anything and Peter has to pay Dfl. 5,000 for damage to Tom's car. Commission. Ellen tells the police that it was Peter who ignored the red light, not Tom. The police charge Peter with failure to stop, and he has to pay Dfl. 5,000 for damage to T o m ' s car.
Appendix B B.1. Scenario I: The nurse
See the Method section of Experiment 3.
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B.2. Scenario 2: The auto-mechanic Omission. A mechanic is repairing a motor of a new type. He does not realize that this motor differs from the old type that he is used to. Because of this, he fails to fix an extra part that is essential for good functioning of the motor. The motor jams and the loss for the business works out to Dfl. 5,000. Commission. A mechanic is repairing a motor of a new type. He does not realize that this motor differs from the old type that he is used to. Because of this, he fixes a part as he would for the old type of motor in this motor. The motor jams and the loss for the business works out to Dfl. 5,000. B.3. Scenario 3: The mechanic Omission. A mechanic has adjusted the traffic lights at 2:00 a.m. in the morning to disturb the traffic as little as possible. In a hurry, because he wants to go to bed, he neglects to reconnect the lights to the system, so that the yellow flashing light keeps burning. The next morning a collision takes place, resulting in a lot of auto body damage, for which the costs are charged to the mechanic's company. Commission. A mechanic has adjusted the traffic lights at 2:00 a.m. in the morning to disturb the traffic as little as possible. In a hurry, because he wants to go to bed, he quickly sets the timer so that the traffic light would start working before rush hour. He sets it at 8:30 a.m. instead of 6:30 a.m., however. The next morning a collision takes place, resulting in a lot of auto body damage, for which the costs are charged to the mechanic's company.
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